For close to a century, scientists have recognized the important role of throughfall and stemflow (precipitation water that falls through plant canopies and runs down plant stems, respectively) in the cycling of materials. These “hydrologic highways” carry atmospherically deposited and canopy-derived materials from the top of the plant canopy to the ground below, thus integrating biological, physical, and chemical processes occurring at the top of and within the canopy and linking above and belowground components of ecosystems. Diverse in nature, abundance, composition, and effects, the materials that flow through plant canopies can be dissolved or particulate, living or nonliving, nutrients or pollutants, beneficial or pathogenic. Yet, despite decades of research, only a small fraction of the components within throughfall and stemflow have been “seen” in studies on material cycles. Thus, our goal in this chapter is to uncover and call attention to the plethora of “unseen” materials in throughfall and stemflow, for example, those that are discarded after filtration and those that remain hidden within precipitation waters. From a biogeochemical standpoint, their quantification is important. Recent research highlights the abundance of particulates, bacterial cells, fungi, and potentially even microplastics in throughfall and stemflow with broader social, economic, and ecological implications for nutrient cycling, soil formation and fertility, decomposition, aquatic ecosystems, climate change, air quality, decontamination, radiation hygiene, species distribution, and disease transmission.
Ponette-González, A. G., Van Stan, J. T., & Magyar, D. (2020). Things seen and unseen in throughfall and stemflow. In Precipitation Partitioning by Vegetation: A Global Synthesis (pp. 70–87). Springer International Publishing. https://doi.org/10.1007/978-3-030-29702-2_5